What Is Prediabetes? Signs, Risks, and What to Do

Understanding what is prediabetes is one of the most important things any adult can do for their long-term metabolic health — yet more than 80 percent of the 96 million American adults who have it don’t know. Prediabetes is a condition in which blood sugar levels are higher than normal but not yet high enough to meet the diagnostic criteria for Type 2 diabetes. It is not a benign in-between state: prediabetes causes real physiological changes, increases the risk of serious complications even before a diabetes diagnosis, and progresses to Type 2 diabetes in a significant proportion of people who do not intervene. But it is also one of the most modifiable conditions in medicine — with the right actions at the right time, prediabetes can be reversed, and the progression to diabetes can be stopped or significantly delayed.

What Is Prediabetes, Exactly?

Prediabetes is defined by blood glucose levels that are elevated above the normal range but below the diabetes threshold. It reflects a state of impaired glucose regulation — specifically, a combination of increasing insulin resistance and reduced beta cell capacity to compensate — that has not yet caused blood sugar to stay chronically above 126 mg/dL fasting (the threshold for diabetes diagnosis) but has already moved it into the danger zone.

Prediabetes is diagnosed by the same blood tests used to diagnose diabetes, applied to a different range of values. Fasting blood sugar between 100 and 125 mg/dL indicates prediabetes (normal is below 100 mg/dL; diabetes is 126 mg/dL or above). On the A1C test, which reflects average blood sugar over the prior two to three months, prediabetes is indicated by values of 5.7 to 6.4 percent (normal is below 5.7%; diabetes is 6.5% or above). On a two-hour oral glucose tolerance test, values of 140 to 199 mg/dL at the two-hour mark indicate prediabetes.

The medical community sometimes distinguishes two subtypes within prediabetes: impaired fasting glucose (IFG), indicated by a fasting blood sugar of 100–125 mg/dL, reflects primarily the liver’s excessive overnight glucose output; and impaired glucose tolerance (IGT), indicated by the elevated two-hour result on the oral glucose tolerance test, reflects primarily a failure of post-meal glucose management. Some people have both. The distinction matters somewhat for predicting the pattern of progression and choosing appropriate interventions, but for most practical purposes, the unified concept of prediabetes is sufficient.

To fully understand prediabetes, it helps to first understand how blood sugar is regulated and what normal levels look like. See our guide on what is blood sugar for a detailed explanation of glucose regulation and the reference ranges that define health and disease.

How Prediabetes Develops

Prediabetes does not appear suddenly. It develops over years through a gradual progression that begins with subtle changes in how cells respond to insulin. In a metabolically healthy person, insulin works efficiently: a modest amount of insulin secreted after meals is sufficient to drive glucose into cells, keeping blood sugar within the normal range. As insulin resistance develops — driven by excess body fat (particularly abdominal fat), physical inactivity, poor sleep, and chronic stress — cells become less responsive to insulin’s signal.

The pancreas compensates by producing more insulin to achieve the same glucose-lowering effect. For a period that may last years, blood sugar stays in the normal range because the extra insulin production makes up for the reduced sensitivity. But this requires the pancreatic beta cells to work much harder than they should. Over time, beta cells begin to show signs of fatigue: they cannot maintain the surge in insulin output indefinitely. As beta cell function begins to decline — even slightly — blood sugar starts to rise above normal after meals and eventually during fasting as well.

By the time fasting blood sugar reaches the prediabetes range, the body has already lost a significant portion of its beta cell reserve. Research suggests that people at the upper end of the prediabetes range (fasting glucose of 110–125 mg/dL or A1C of 6.0–6.4%) have already lost approximately 50 percent of their beta cell function compared to people with normal glucose tolerance. This is why early detection and early action are so important: the further into the prediabetes range, the less beta cell reserve remains and the harder it is to prevent progression.

Who Is at Risk for Prediabetes?

Prediabetes risk factors are largely the same as those for Type 2 diabetes, which makes sense since prediabetes is the intermediate stage in that progression:

• Overweight or obesity: Excess body fat — especially visceral fat stored around the abdominal organs — is the single strongest modifiable risk factor for insulin resistance and prediabetes. Even modest weight gain over time significantly increases risk
• Physical inactivity: Sedentary behavior reduces muscle sensitivity to insulin by decreasing the activity of glucose transporter proteins. Even without weight loss, regular exercise significantly improves insulin sensitivity
• Age 45 or older: Both insulin sensitivity and beta cell function decline naturally with aging. The American Diabetes Association recommends prediabetes screening for all adults beginning at age 45
• Family history of Type 2 diabetes: Having a parent or sibling with Type 2 diabetes increases risk by two to three times, reflecting shared genetic variants that affect insulin sensitivity and beta cell function
• Prior gestational diabetes: Women who developed gestational diabetes during pregnancy retain a lifetime elevated risk of prediabetes and Type 2 diabetes due to the metabolic stress the pregnancy placed on their beta cells
• Polycystic ovary syndrome (PCOS): A hormonal condition in which insulin resistance is a core feature, affecting up to 10 percent of women of reproductive age
• Race or ethnicity: Black, Hispanic, Native American, Asian American, and Pacific Islander adults develop prediabetes and Type 2 diabetes at higher rates than white Americans, often at lower body weights, reflecting differences in metabolic risk profiles
• High blood pressure or abnormal cholesterol: Conditions that frequently co-occur with insulin resistance as part of a broader metabolic syndrome
• Sleep disorders: Poor or insufficient sleep directly impairs insulin sensitivity. Even a single night of inadequate sleep reduces insulin sensitivity measurably

Does Prediabetes Cause Symptoms?

For most people, prediabetes causes no noticeable symptoms at all. This is one of the most dangerous aspects of the condition: it can exist and progress silently for years, causing physiological changes and accumulating damage without producing the thirst, urination, and fatigue that often prompt someone to see a doctor. The absence of symptoms is why routine blood screening — not waiting for symptoms to appear — is the only reliable way to detect prediabetes.

Some people at the higher end of the prediabetes range, or who have had it for several years, may begin to notice subtle signs: mild increased thirst, slightly more frequent urination than usual, or fatigue after carbohydrate-heavy meals. Darkened skin patches in body folds and creases — a condition called acanthosis nigricans, appearing on the neck, armpits, or groin — can indicate underlying insulin resistance and are sometimes visible before blood sugar rises significantly. But these signs are nonspecific and easy to dismiss, and many people with fully established prediabetes have none of them.

This is why the American Diabetes Association’s recommendation to test all adults starting at age 45 exists, and why earlier testing is recommended for anyone with one or more risk factors listed above. Getting a simple fasting blood test or A1C test at a routine physical is the most reliable way to know where you stand.

What Happens If Prediabetes Is Left Untreated?

Without intervention, prediabetes frequently progresses to Type 2 diabetes. Studies suggest that approximately 15 to 30 percent of people with prediabetes develop Type 2 diabetes within five years, and up to 70 percent eventually develop it over a lifetime. However, this progression is neither inevitable nor uniform: many people with prediabetes, particularly those at the lower end of the range, remain stable for years or even return to normal glucose tolerance without formal intervention — particularly if they make lifestyle changes independently.

Even in the prediabetes range, before Type 2 diabetes is diagnosed, elevated blood glucose begins causing physiological harm. Research shows that people with prediabetes already have elevated cardiovascular risk compared to those with normal glucose levels. The damage to small blood vessels and nerves that eventually produces diabetic complications begins in the prediabetes range, not only after the diagnostic threshold for diabetes is crossed. Peripheral neuropathy, for example, is detectable in some people with prediabetes. This is why prediabetes is not a benign waiting room — it is a condition that warrants prompt, meaningful action.

The Evidence for Reversing Prediabetes

The evidence that prediabetes can be reversed — and that this reversal prevents or substantially delays Type 2 diabetes — is among the strongest in preventive medicine. The landmark Diabetes Prevention Program (DPP), a large randomized clinical trial funded by the National Institutes of Health, enrolled more than 3,000 adults with prediabetes and demonstrated that structured lifestyle intervention reduced progression to Type 2 diabetes by 58 percent over three years. This result was significantly more effective than treatment with the medication metformin (31 percent reduction) and has been replicated in multiple studies across different countries, cultures, and healthcare systems.

The lifestyle intervention in the DPP was not extreme. Participants were asked to achieve and maintain a 7 percent reduction in body weight (for a 200-pound person, that is 14 pounds) through reduced calorie and fat intake, and to engage in at least 150 minutes of moderate-intensity physical activity per week — approximately 30 minutes of brisk walking five days a week. These are achievable goals that do not require drastic dieting or intense exercise regimens, though consistency over time is essential.

The DPP Outcomes Study, which followed participants for up to 15 years after the trial, found that lifestyle intervention continued to delay or prevent diabetes — not just during the study period but for years afterward. People who maintained their lifestyle changes sustained a meaningfully lower rate of diabetes diagnosis compared to those who did not. This underscores the cumulative, long-term nature of the benefit: it is not a one-time intervention but an ongoing shift in metabolic habits.

Practical Steps to Reverse Prediabetes

If you have been diagnosed with prediabetes, the following evidence-based actions offer the most meaningful impact on your trajectory:

Lose a modest amount of weight if you are overweight: Even 5 to 7 percent of body weight — 10 to 14 pounds for a 200-pound person — produces measurable improvements in insulin sensitivity and fasting blood sugar. You do not need to reach an “ideal” body weight for prediabetes reversal; early, modest weight loss is where most of the benefit lies.

Move more — especially after meals: Regular physical activity improves insulin sensitivity independently of weight loss. A mix of aerobic exercise (brisk walking, cycling, swimming) and resistance training (weights, resistance bands) has the most comprehensive effect on insulin sensitivity. Brief walks after meals — even 10 to 15 minutes — have been shown to meaningfully reduce post-meal blood sugar peaks.

Restructure your carbohydrate choices: You do not need to eliminate carbohydrates, but replacing refined carbohydrates and added sugars with fiber-rich alternatives dramatically changes how food affects blood sugar. Legumes, non-starchy vegetables, whole grains, and most fruits produce gradual, modest glucose rises compared to white bread, pastries, sugary drinks, and processed snack foods. Eating protein and fat alongside carbohydrates further blunts glucose peaks.

Prioritize sleep: Consistently sleeping seven to nine hours per night is among the most underappreciated interventions for insulin sensitivity. Chronic sleep restriction of even one to two hours per night significantly worsens glucose metabolism and can counteract the benefits of diet and exercise efforts. Treating sleep apnea — which causes metabolic disruption through repeated nighttime oxygen deprivation — is particularly important for metabolic health.

Reduce sedentary time: Beyond planned exercise, reducing the total amount of time spent sitting continuously throughout the day improves glucose metabolism. Breaking up long periods of sitting with brief standing or walking breaks — even two to three minutes every 30 minutes — reduces post-meal glucose levels measurably in research settings.

Monitor your progress: Follow-up A1C or fasting glucose testing every six to twelve months allows you to track whether your efforts are moving your numbers in the right direction and provides early warning if blood sugar continues rising despite intervention. For guidance on at-home monitoring options, see our guide on home blood sugar monitoring.

When Medication Is Considered for Prediabetes

While lifestyle intervention is the first-line approach for prediabetes, medication may be considered in some situations — particularly for people who are unable to achieve sufficient weight loss or activity levels through lifestyle changes alone, or who have very high-risk features such as an A1C close to 6.4 percent or a history of gestational diabetes.

Metformin — the most widely used diabetes medication — has been shown to reduce prediabetes progression to Type 2 diabetes by approximately 31 percent in the DPP, making it less effective than lifestyle intervention but still meaningful, particularly for younger adults and those with a higher BMI. It is generally safe, inexpensive, and well-tolerated, and is sometimes prescribed as an adjunct to lifestyle changes rather than a replacement for them. The decision to add medication to lifestyle intervention is individualized and should be made in partnership with a healthcare provider who can assess the full metabolic picture.

A prediabetes diagnosis is one of the clearest early warning signals the body provides about metabolic trajectory. Acting on it is not optional for those who want to avoid the progressive complications of diabetes — but it is highly actionable. The gap between prediabetes and Type 2 diabetes is where intervention has the most power, and the evidence that it works is among the strongest available in preventive medicine.

The Role of Diet in Reversing Prediabetes

Diet is the single most powerful lever available to people trying to reverse prediabetes, because what you eat directly determines how much glucose enters the bloodstream, how quickly it rises, and how much insulin the pancreas must produce in response. The goal is not to eliminate all carbohydrates — carbohydrates are an important macronutrient and the primary fuel for the brain and working muscles — but to shift the quality of carbohydrates consumed and moderate the overall glucose load that reaches the bloodstream at any one time.

The Mediterranean dietary pattern — emphasizing vegetables, legumes, whole grains, fish, olive oil, nuts, and modest amounts of fruit and dairy, with limited red meat and minimal added sugar — has among the strongest evidence for improving insulin sensitivity and reducing diabetes risk. Large randomized trials have shown that following a Mediterranean-style diet reduces new diabetes diagnoses by 30 to 50 percent compared to a low-fat control diet, and it also reduces cardiovascular risk significantly — important because metabolic syndrome and prediabetes frequently co-occur with elevated cardiovascular risk.

Specific dietary elements with the strongest evidence for prediabetes management include:

• Dietary fiber: Soluble fiber from legumes, oats, apples, pears, and many vegetables slows glucose absorption and reduces post-meal blood sugar peaks. Insoluble fiber from whole grains improves insulin sensitivity over time. Aim for at least 25 to 35 grams of total fiber per day — substantially more than the average American consumes
• Vinegar and fermented foods: Acetic acid (the active compound in vinegar) slows gastric emptying and improves insulin sensitivity. Adding vinegar-based salad dressings or consuming fermented foods like yogurt and kimchi regularly may contribute modestly to better glucose control
• Minimizing sugar-sweetened beverages: Liquid calories from sodas, juices, sports drinks, and sweetened coffees produce the most rapid and pronounced blood sugar spikes of any food category and are among the most strongly associated dietary factors with Type 2 diabetes risk. Replacing them with water, unsweetened tea, or coffee is one of the highest-impact single dietary changes available
• Meal timing and composition: Eating the largest portion of daily carbohydrates earlier in the day, when insulin sensitivity is naturally higher, may reduce overall glucose exposure compared to front-loading calories at dinner. Combining carbohydrates with protein, fat, and fiber at every meal blunts glucose absorption compared to eating carbohydrates alone

The Connection Between Prediabetes and Other Health Conditions

Prediabetes rarely exists in isolation. It is strongly associated with a cluster of metabolic abnormalities that together define metabolic syndrome: abdominal obesity, high blood pressure, elevated triglycerides, low HDL cholesterol, and impaired fasting glucose. People with prediabetes frequently have several of these conditions simultaneously, which together dramatically elevate the risk of cardiovascular disease — independently of the diabetes risk that prediabetes itself confers.

This means that a prediabetes diagnosis is often an opportunity to assess and address the entire metabolic picture, not just blood sugar alone. Blood pressure management, cholesterol treatment, sleep apnea screening (obstructive sleep apnea both causes insulin resistance and is exacerbated by the abdominal obesity that commonly accompanies prediabetes), and stress reduction all contribute to reversing the underlying insulin resistance that prediabetes reflects.

Nonalcoholic fatty liver disease (NAFLD) — the accumulation of fat in liver cells — is another condition that frequently co-occurs with prediabetes and insulin resistance. The liver plays a central role in glucose regulation, releasing glucose between meals and clearing it after meals, and a fatty, inflamed liver does this job less effectively, contributing to higher fasting blood sugar levels. Interventions that reduce liver fat — most effectively weight loss and reduced sugar intake, particularly fructose — improve liver function and glucose regulation simultaneously.

For adults who receive a prediabetes diagnosis alongside other metabolic findings, the combined lifestyle intervention that addresses weight, activity, diet quality, and sleep simultaneously is far more effective than targeting any single risk factor in isolation. The body’s metabolic systems are interconnected: improving sleep improves insulin sensitivity, which reduces appetite and makes weight loss easier, which reduces liver fat and abdominal fat, which further improves insulin sensitivity. This positive cascade is exactly what makes well-implemented lifestyle change so powerful — and so much more effective than addressing one variable at a time.

Setting Realistic Expectations

One of the most important things to understand about reversing prediabetes is that the goal is metabolic improvement, not perfection. Not everyone with prediabetes will return their A1C completely to normal — factors including age, duration of prediabetes, degree of beta cell loss, and genetic predisposition all affect how much improvement is achievable. But substantial improvement — moving from the high end of the prediabetes range to the low end, or from prediabetes to normal — dramatically reduces the risk of progression to diabetes and the development of complications.

Progress is best tracked through repeat A1C or fasting glucose testing every six to twelve months. If your numbers are moving in the right direction with lifestyle changes, that is success — even if they have not yet normalized. If they are rising despite your best efforts, that is important information that warrants a conversation with your doctor about adding medication support.

The fundamental message of the evidence is clear: prediabetes is not a sentence — it is a signal. It is the body communicating, clearly and measurably, that its current metabolic trajectory needs to change. The tools to change it are well-established, accessible, and effective. The time to act on them is now, before the opportunity that prediabetes represents has closed.

Sources: American Diabetes Association. Standards of Medical Care in Diabetes — 2024. Diabetes Care. 2024;47(Suppl 1):S20–S42. • Knowler WC, et al. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. New England Journal of Medicine. 2002;346(6):393–403. • Centers for Disease Control and Prevention. National Diabetes Statistics Report, 2022. CDC; 2022.